IAEA only finds light damage at Onagawa

Although the Great East Japan Earthquake and tsunami wrecked the Fukushima No. 1 plant in Fukushima Prefecture, the younger Onagawa plant in neighboring in Miyagi was “remarkably undamaged” by the violent temblor and tsunami and safely shut down, experts from the International Atomic Energy Agency said Friday.

Given a quake of this magnitude, “we would have expected the plant to have more damage, and that was not the case,” Sujit Samaddar, who led the 19-member team, told reporters in Tokyo, wrapping up their two-week on-site probe.

From its visual investigation, the IAEA team did not find any signs that cooling pipes or other critical equipment were damaged or caused coolant loss at the 28-year-old plant, said Samaddar, who heads the IAEA International Seismic Safety Centre.

The IAEA team arrived last month to see how the magnitude 9.0 temblor on March 11, 2011, affected the Onagawa plant, which runs three reactors on the Pacific coast about 120 km north of the 40-year-old Fukushima plant.

Whether the quake itself damaged the pipes and cooling systems at Fukushima No. 1, which was swamped by tsunami and suffered three meltdowns, has been hotly debated since a Diet-appointed investigative panel suggested that possibility over denials by Tokyo Electric Power Co.

Samaddar stressed that while his team did not find any trace of such damage, its investigation didn’t cover everything in great detail. He said the team only conducted visual checks — of samples of equipment — because time was limited.

Asked what the main differences are between Tepco’s Fukushima plant and Tohoku Electric Co.’s Onagawa plant, Samaddar said various factors and data need to be scrutinized and that it will take time to find an answer.

The killer earthquake registered as a weak 6 on the Japanese seismic intensity scale to 7 at Onagawa, which saw tsunami reach about 13 meters high.

Samaddar said there was minor damage from the quake, including cracks in the turbine buildings, but that none of it would have led to a nuclear calamity like Fukushima.

The team investigated structural elements of the plant and the systems safeguarding the reactors, and held interviews with some of the engineers.

The data and experience collected from the investigation will be added to the IAEA’s database to improve safety at nuclear power plants worldwide.